This invention relates to magnetic bubble (domain) assemblies and more particularly to a new and improved bubble memory package arrangement.
A magnetic bubble package comprises one or more chips or modules containing a thin layer of garnet-like material formed on a substrate and disposed between the bias magnets to provide a bias field normal to the plane of the substrate to establish and maintain bubbles in the garnet-like material. For bubble movement (propagation) in the plane of garnet-like material, sinusoidal type field drive coils, provide rotational in-plane magnetic fields and surround the substrate. Means are also provided to interconnect the chips to one another, if there is more than one chip in the package, to the control circuitry for performing various bubble manipulations in the chips and to connect the memory to the outside world.
In the prior art, this latter means for connecting the chip to other chips and to the outside world comprised a rigid printed circuit board on which the chips were mounted and the latter was connected by wires or other suitable conductors to pins or other connectors. This required an interconnection between the chips and the printed circuit board and another connection between the printed circuit board and the pins-- all of which introduce possible malfunctions (open or cold solder joints) and increased the overall thickness of the package.
Accordingly, it is one of the objects of this invention to provide a new and improved means to interconnect the chips to one another and to the control circuitry in a bubble memory package device which illuminates a number of interconnections and is slimmer than the prior art systems.
Too, conventionally, in order to provide a magnetic gradient or differential between the bias magnets and the chips to insure proper bubble manipulation and propagation, it was common practice to taper the bias magnets themselves on one side, i.e., to form an incline on one side of the bias magnets facing the chips, to provide a magnetic differential gradient in one direction. A typical example of this prior art is shown in the U.S. Pat. No. 4,027,298. However, one of the defects in this was the difficulty in placing the taper on the surface of the magnets because of the necessary grinding and honing of the magnetic material. This was expensive and increased the cost of the package. Too, such an arrangement did not allow for any adjustments relative to plane of the yoke or substrate and required the components to have rather rigid tolerance requirements.
Accordingly, it is still another object of this invention to provide a bubble memory package with a means of providing a magnetic gradient to the bubble chips without utilizing tapered bias magnets which heretofore have increased the cost of manufacture of the bubble assemblies and have rather rigid tolerance requirements.
In addition to the foregoing, it is well known that it is desirable to maintain the space between the assembled components i.e., coils, chips, interconnection circuitry, etc. as small as possible for a number of reasons including reducing the power requirements of the field drive coils. However, it is also recognized that the largest source of heat comes from the field drive coils during operation and that, unless this heat is dissipated or controlled, the operating characteristics of the magnets and the chips are materially and sometimes adversely affected. It is also well known that it is especially desirable to maintain the temperature of the bias magnets as close as possible to the temperatures of the chips so that the bias field will remain constant relative to the chips thus not disrupting the size or position of the bubbles.
The control or management of this heat and the distribution thereof throughout the bubble package is disclosed and claimed in the copending U.S. Pat. Application of W. T. Layton, entitled "THERMAL CONTROL MEMBER, BUBBLE MEMORY", supra. In this application, it is shown that compliant members of a selected material are placed on the side of the yoke opposite to the bias magnets and, depending upon the material selected, dissipate control heat generated by the drive coils. These compliant units also perform the function of compensating for any misalignment or tolerance variations in or among the components due to the resiliency of the units. Also, to further aid in the management of the heat within the package, reference is made also to the U.S. Patent Application copending herewith to Layton entitled "BUBBLE MEMORY PACKAGE WITH THERMAL CONTROL" in which thermal control units are shown to engage the sides of the drive coils and together with flexible heat conductor members complete the thermal control of the package. The place in which the ends of the flexible members are located largely depend upon the desired results. The application, supra, teaches the use and disposition of the ends of these flexible members.
In connection to this thermal magnetic technique, it is important to point out that separate tapers, while providing a magnetic gradient and compensation for possible out of tolerance components, also are made of a material having controlled thermal conductive properties so they too aid in the management of the heat within the package.
Thus, this invention teaches how these thermal management means can function with other components of the package including the aforesaid tapers having controlled thermal conductivity to provide a bubble memory package which is less expensive to manufacture and yet is thermally efficient.
Accordingly, it is still another object of this invention to provide a package with means for controlling the heat generated in the package during operation and to do so in an inexpensive manner.